There is a need in this art to be able to compact material which includes components of various sizes, densities, elasticity, moisture content etc. Material of the type mentioned by way of introduction is often massive and bulky and needs to be compressed or compacted in order to be capable of being handled and transported in an economically viable manner Such needs occur, for example, in industrial operations and in municipal waste disposal, for example in refuse collection. For wet matter, it is also often desirable to reduce the moisture content of the material in connection with its compression (compaction).
Prior art technology calls for the employment of hydraulic compactors for compacting material of the above-disclosed type. Hydraulic compactors are expensive, unwieldly and heavy, in addition to which the reduction in volume which is obtained is relatively slight. As regards, for example, domestic or commercial waste, the reduction involved is no greater than a factor of 3. This slight degree of compaction is because all material to be found in the transport container is compacted at the same time.
For compaction purposes, use is also made of screw compactors consisting of a mechanical shaft which is fitted with thread blades and is surrounded by a tubular casing. Compaction is achieved in that the screw compactor presses the material into a container which is filled in due course. When the container has been filled, the screw compactor is employed to continue to force material into the container and there is thereby obtained a certain degree of compression of the material which is located in the container. However, the level of compaction is relatively slight; nor does this technique exceed a level of compaction of a factor 3. The explanation for the slight degree of compaction is that those pressure forces which are exercised by the screw compactor are absorbed by substantially all material located in the container, with the result that those forces which act on each individual component will, naturally be relatively slight. Screw compactors have relatively low capacity in relation to their size, suffer from difficulties in handling large objects and require considerable power for their operation. In addition, screw compactors are large and heavy, as well as being expensive in both purchase and operation.
Spiral compactors are also employed for compacting material. The term spiral compactor is here taken to signify compactors including a spiral which is rotary about its longitudinal axis, which lacks a mechanical shaft and which includes a spiral or helical blade stood on its end and surrounded by a casing. In such instance, the spiral and the casing form a precompaction zone where compaction of the material commences. In the precompaction zone the spiral has an outer diameter which is slightly less than the inner diameter of the casing. Thereby, the spiral closely approaches (with slight clearance) the surrounding casing. The precompaction zone is followed, in the direction of displacement of the material, by a region which has no spiral and in which the final compaction of the material takes place.
Spiral compactors have a relatively simple design and construction which results in low practical and running costs, at the same time as the degree of compaction is considerably better than the above-disclosed factor of 3. The construction of spiral compactors described in the preceding paragraph (slight clearance between casing and spiral) entails, however, the disadvantage that, on varying material size, the material is occasionally jammed between the spiral and the casing. In particular when large-pieces of material are involved, blockages readily occur, with resultant operational disturbance or operational disruption.